facebook/react

"Should not already be working" in Firefox after a breakpoint/alert

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#17355 opened on Nov 13, 2019

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 (132 comments) (85 reactions) (0 assignees)JavaScript (245,029 stars) (51,039 forks)batch import
Difficulty: mediumType: BugType: Needs Investigationgood first issue

Description

Do you want to request a feature or report a bug? Bug

What is the current behavior? I'm seeing "Error: Should not already be working" after upgrading to React 16.11

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

This is exclusively happening on an older version of Chrome, 68.0.3440 on Windows 7

I was unable to reproduce this in a VM environment but our Sentry is getting littered with these errors.

I know it's a long shot, but I wasn't able to find any information about this error anywhere, just a reference in the error codes file in react, so thought it would be a good idea to report this just in case. Curious if anyone has seen this.

Contributor guide

Tech stack
javascriptreact
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
React fiber internalsReact error handlingBrowser debugging
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the error message 'Should not already be working' which is defined in the React error codes file (likely scripts/error codes.json). Look into the React fiber scheduler code (e.g., ReactFiberWorkLoop.js) to understand when this invariant is triggered. Reproduce using the reported conditions in older browsers (Chrome 68 on Windows 7). Check if there were any related commits or PRs addressing this error in later versions. Consider if this is a race condition with breakpoints/alert. Also review the comments in the issue for troubleshooting attempts and potential fixes.